A transmitter coil of a magnetic resonance imaging (MRI) apparatus is designed to accept as input a radio frequency (RF) pulse and emit a radio frequency (RF) magnetic field (B1) to an object.
Some MRI apparatus have plural transmission channels. It is important for this type of MRI apparatus to perform control such that the RF pulse inputted to each transmission channel will have a desired amplitude and phase.
However, in calibrating the amplitude and phase inputted to each transmission channel, a method which uses the amplitude and phase of a signal outputted by a unit configured to generate transmit pulses cannot take into consideration the influence caused by all transmission paths of the transmit pulses. For example, the influence of a signal cable running from the unit to the transmission channel is not reflected.
Consequently, it is not possible to keep track of amplitude losses and phase shifts of the RF pulse accurately, which could disable B1 distortion correction, resulting in increased RF strength. Also, if adjustments are made using a network analyzer or the like to correct the phase shifts, the adjustments will take time, resulting in greatly reduced convenience.
Also, when the amplitude and phase of input to each transmission channel are calibrated using a method which uses output from an RF measurement pickup coil installed in a gantry aside from a receiver coil, this means that there are three types of coils in the gantry: the transmitter coil, receiver coil, and pickup coil. In this case, it becomes difficult to make adjustments due to interference among the coils. Also, increases in the number of parts will increase a failure rate, size, and cost.